The Iron Project \& The Opacity Project: Iron ions at the solar radiative-convection boundary - Fe~XVII, Fe~XVIII, Fe~XIX*

Iron is the dominant heavy element that determines radiation transport

in stellar interiors. In particular, a few iron ions, constitute the

abundance and opacity of iron at the solar radiative-convection zone

boundary at the base of the convection zone (BCZ) where the temperature

is $2.11 \times 10^6$K and the electron density is $3.1 \times 10^{22}$cc.

Opacity calculations require large-scale atomic calculations for many

excited levels and bound-bound and bound-free transtions, including

those of very highly lying levels.

Together, Fe~XVII-XIX contribute 85\% of iron with ion fractions 20\%,

39\% and 26\% each respectively, at BCZ conditions.

Extensive R-matrix calculations are reported using large wavefunction

expansions for the (e-ion) system: 216 fine structure levels of the

core ion for Fe~XVII, 276 levels for Fe~XVII and 58 LS states for

Fe~XIX n=2,3,4.

Extensive sets of energy levels, oscillator strengths, and photoionization

cross sections of the 3 ions have been obtained. Selected results are

presented and the importance of physical features in plasma opacities is

described.